“This case has already been won in arbitration and anything beyond that, I would refer you to the president’s outside counsel,” said Ms Sanders, who insisted that Mr Trump denies Ms Daniels’s allegations.

At a White House press briefing Ms Sanders was pressed further on who won the arbitration and when. The spokeswoman replied gnomically: “By the president’s personal attorneys and for details on that I would refer you to them.

“I can share that the arbitration was won in the president’s favour, and I would refer you to the president’s outside counsel on any details beyond that.”

The disclosure implies that arbitration was used as a simpler, less costly alternative to litigation.

Soon after the briefing, Ms Daniels’s lawyer, Michael Avenatti, reportedly dismissed Ms Sanders’s claim. Jim Rutenberg, media columnist at the New York Times, tweeted: “Stormy Daniels lawyer, @MichaelAvenatti responds to me re Sanders’ statement Trump won at arbitration: ‘yeah and he also won the popular vote’.”

Mr Trump received almost three million fewer votes in the US presidential election of 2016 than his main rival, Hillary Clinton, but won the presidency under the country’s Electoral College votes system.

On Tuesday Ms Daniels filed a lawsuit in Los Angeles against Mr Trump, arguing that his longtime personal lawyer Michael Cohen tried to silence her “through the use of an improper and procedurally defective arbitration proceeding hidden from public view”.

Payment

Ms Daniels contends that a non-disclosure agreement she signed days before the 2016 presidential election, which blocked her from discussing the alleged sexual encounters, is “null and void and of no consequence” because Mr Trump did not personally sign it.

Mr Cohen has said he paid the actress $130,000 out of his own pocket as part of the agreement. He has also said that “neither the Trump Organization nor the Trump campaign was a party to the transaction with Ms Clifford, and neither reimbursed me for the payment, either directly or indirectly”.

Ms Sanders was asked repeatedly about whether Mr Trump had knowledge of the payment by Mr Cohen. She said: “I’ve had conversations with the president about this. And, as I outlined earlier, that this case has already been won in arbitration and that there was no knowledge of any payments from the president, and he’s denied all of these allegations.”

Meanwhile Mr Avenatti said on television on Wednesday that Ms Daniels wanted “to set the record straight”. He told NBC there was “no question” Mr Trump knew about the agreement, though he did not offer any proof.

Mr Avenatti said Ms Daniels was not looking to profit from her story. But he told CBS: “I don’t know whether she’s going to ultimately seek payment or not.”

Ms Daniels alleges that she began the “intimate relationship” with Mr Trump in 2006 and that it continued “well into the year 2007”, according to the lawsuit. She said it included encounters in Lake Tahoe, Nevada, and Beverly Hills, California. Mr Trump married Melania Trump, now the first lady, in 2005. – Guardian